1. Technical Field
The present invention relates to a technology of generating pulse width modulation signals for modulating laser beams according to image data.
2. Related Art
Currently, there is a proposal of a laser scan type projector which displays images by laser beams. Also, a technology of pulse width modulation (PWM) which varies duty ratio of pulse waves having predetermined cycles is known as a laser beam modulation system.
According to the laser scan type projector, the optical path length between a light source and a screen differs according to the drawing position on the screen, which requires the drawing rate to be varied. However, when the laser scan type projector uses PWM signals generated by the PWM system and thus having fixed cycles, modulation of laser beams does not come up with the drawing rate. Thus, images cannot be accurately displayed.
A laser scan type projector disclosed in JP-A-2007-140009 adopts the pulse width modulation (PWM) system. According to this projector, the optical path length is fixed by connecting the same number of optical fibers as that of pixels of images displayed on a screen to the back surface of the screen. In this case, however, the device structure becomes complicated.